Since the issuance of U.S. Pat. No. 3,028,365 in April of 1962, aromatic polycarbonate has become well known and accepted as a thermoplastic resin suitable for a wide variety of uses including injection molding, extrusion and film formation. The chemistry, synthesis, properties and applications of these polycarbonates are extensively discussed in Chemistry and Physics of Polycarbonates by Schnell, Interscience, 1964 and Polycarbonates by Christopher and Fox, Reinhold, 1962. Although polycarbonates have some inherent flame resistance, being self-extinguishing, ever more demanding requirements of flame-resistance have spawned numerous attempts to increase this property. Two general approaches have been followed.
One approach has been to add substantial amounts of halogen, particularly bromine or chlorine, to polycarbonate compositions. The halogen can be carried by polycarbonate polymer chains as in U.S. Pat. Nos. 3,751,400 and 3,334,154 or by a monomeric compound as in U.S. Pat. No. 3,382,207.
However, the presence of substantial amounts of halogen has been found to be detrimental to the properties of the polycarbonate and numerous additives such as those proposed in U.S. Pat. Nos. 3,647,747 and 3,733,295 have been proposed to overcome these detrimental effects.
Flame retardant polycarbonate compositions containing polytetra-fluoroethylene (PTFE) are known in the art. U.S. Pat. No. 4,391,935 discloses such compositions which also include certain salts. U.S. Pat. No. 3,294,871 disclosed a process for producing molding compositions containing PTFE and a thermoplastic polymer entailing blending the thermoplastic polymer with a latex of the PTFE to produce a dispersed, substantially homogeneous mixture of the PTFE and a thermoplastic polymer and recovering the composition by removing the volatiles therefrom. Among the polymers polycarbonates are listed at col. 3, lines 6–8. The disclosed compositions are said to offer advantages in terms of impact strength, melt index, coefficient of friction, low water permeability and increased HDT.
U.S. Pat. No. 3,005,795 discloses compositions containing PTFE resin in a form of finely divided microfibrous and submicrofibrous particles. Polycarbonates are disclosed at col. 3, lines 18–19 as suitable matrix.
The usage of any of a variety of salts—notably perfluoroalkane sulfonate salts of alkali metal or alkaline earth metal—with and without PTFE as a flame retardant for polycarbonate has been disclosed in U.S. Pat. Nos. 3,775,367; 4,469,833; 4,626,563; 4,626,563; and 4,649,168. Alkali metal salts of sulfonic acids were disclosed in U.S. Pat. No. 4,469,833 to be flame retardant additives in the context of polycarbonate compositions containing structural units derived from thiodiphenol.
U.S. Pat. No. 4,220,583 disclosed flame retardant polycarbonate compositions containing partially fluorinated polyolefin and organic salts of alkali metal or alkaline earth metals. The salts include the ones disclosed in the following publications:
U.S. Pat. No. 3,933,734 which discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of either monomeric or polymeric aromatic sulfonic acids, or mixtures thereof. U.S. Pat. No. 3,948,851 that discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of either monomeric or polymeric aromatic sulfonesulfonic acids, or mixtures thereof.
U.S. Pat. No. 3,926,908 which discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of sulfonic acids of aromatic ketones, or mixtures thereof. U.S. Pat. No. 3,919,167 which discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of heterocyclic sulfonic acids, or mixtures thereof. U.S. Pat. No. 4,066,618 which discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of a halogenated non-aromatic carboxylic acid or mixtures thereof. U.S. Pat. No. 3,909,490 which discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of sulfonic acids of aromatic sulfides, or mixtures thereof. U.S. Pat. No. 3,953,396 which discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of either monomer or polymeric aromatic ether sulfonic acids, or mixtures thereof. U.S. Pat. No. 3,931,100 which discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of aliphatic and olefinic sulfonic acids, and mixtures thereof. U.S. Pat. No. 3,978,024 which discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of either monomeric or polymeric phenol ester sulfonic acids, or mixtures thereof. U.S. Pat. No. 4,069,201 which discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of unsubstituted or halogenated oxocarbon acids, or mixtures thereof. U.S. Pat. No. 3,953,399 which discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of sulfonic acids of monomeric and polymeric aromatic carboxylic acids and esters, and mixtures thereof. U.S. Pat. No. 3,917,559 which discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of halocycloaliphatic aromatic sulfonic acids. U.S. Pat. No. 3,951,910 which discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of either monomeric or polymeric aromatic amide sulfonic acids, or mixtures thereof. U.S. Pat. No. 3,940,366 which discloses a flame retardant polycarbonate composition comprising an admixture of an aromatic polycarbonate and a flame retardant additive which can be the metal salts of either monomeric or polymeric aromatic sulfonic acids, or mixtures thereof.
German published specification DE-OS 33 22 260 discloses PTFE co-precipitated with ABS and added to polycarbonate. Related technologies are disclosed in EP-OS 0,154,138 which disclosed a system entailing ABS and PTFE, DE-OS 34 17 476 which discloses the system of polyamides and PTFE and DE-OS 34 18 750 which concerns the system of ABS co-precipitated with PTFE. Also of relevance are DE-OS 34 20 002, DE-OS 34 22 862, DE-OS 35 12 638 (equivalent to EP-OS 0,174,493), DE-OS 29,48 439 and U.S. Pat. No. 4,208,489.
Also relevant in the present context is U.S. Pat. No. 4,753,994 which disclosed flame retardant polycarbonate compositions containing a co-precipitate of polycarbonate and fluoropolymer. Also relevant is EP 899 303 for its disclosure of a flame retardant polycarbonate composition which contains fluoropolymer resin particles that are encapsulated by thermoplastic SAN copolymer. U.S. Pat. No. 5,773,493 is noted here for its disclosure of a method of dispersing additives such as PTFE in a thermoplastic polymer and the use of the product of the inventive method in preparing molding compositions.
Translucent and flame-retardant polycarbonate compositions containing polycarbonate, a partially fluorinated polyolefin, and an organic alkali (or alkaline earth) metal salt were disclosed in U.S. Pat. No. 4,220,583.
EP-A-0,166,187 describes a powder composition containing PTFE. The powder is obtained by mixing a dispersion of PTFE with latex of grafted polymer, for example an acrylonitrile-butadiene-styrene grafted polymer, filtering and drying in order to obtain a powder.
U.S. Pat. No. 5,804,654 disclosed PTFE containing powder and free flowing PTFE that is at least partially encapsulated by a polymer or copolymer. Polycarbonate compositions that contain the PTFE and any of several flame-retardants additives have been disclosed.